docs: def set_chebyshev_approximators(self, deg_forward=50, deg_backwards=200):        
          r'''Method to derive and set coefficients for chebyshev polynomial 
          function approximation of the height-volume and volume-height
          relationship. 
          
          A single set of chebyshev coefficients is used for the entire height-
          volume and volume-height relationships respectively. 
          
          The forward relationship, `V_from_h`, requires
          far fewer coefficients in its fit than the reverse to obtain the same
          relative accuracy. 
          
          Optionally, deg_forward or deg_backwards can be set to None to try to 
          automatically fit the series to machine precision.
          
          Parameters
          ----------
          deg_forward : int, optional
              The degree of the chebyshev polynomial to be created for the
              `V_from_h` curve, [-]
          deg_backwards : int, optional
              The degree of the chebyshev polynomial to be created for the
              `h_from_V` curve, [-]
          '''
          from fluids.optional.pychebfun import Chebfun
          to_fit = lambda h: self.V_from_h(h, 'full')
          
          # These high-degree polynomials cannot safety be evaluated using Horner's methods     
          # chebval is 2.5x as slow but 100% required; around 40 coefficients results are junk
          self.c_forward = Chebfun.from_function(np.vectorize(to_fit), 
                                                 [0.0, self.h_max], N=deg_forward).coefficients().tolist()
  
          self.V_from_h_cheb = lambda x : chebval((2.0*x-self.h_max)/(self.h_max), self.c_forward)
          
          to_fit = lambda h: self.h_from_V(h, 'brenth')
          self.c_backward = Chebfun.from_function(np.vectorize(to_fit), [0.0, self.V_total], N=deg_backwards).coefficients().tolist()
          self.h_from_V_cheb = lambda x : chebval((2.0*x-self.V_total)/(self.V_total), self.c_backward)
          self.chebyshev = True